P. N. Tandon

Theg-factor of the 659 keV level in117In

We have measured theg-factor of the 659 keV, 3/2+, state in117In, using time differential perturbed angular correlation technique. The spin precession of this state was measured in an external field of 20·2 kG. The values of the Larmor precession frequencyω and theg-factor are obtained to be (60·1±0·3)106 rads/sec and 0·625±0·007 respectively.

Electromagnetic properties of low lying levels in75As

Theg-factors of the 265 and 280 keV levels have been measured to be 0.61±0·16 and 0·30±0·05 respectively. The PAC technique was used for the measurements. In addition, the half-life of the 280 keV level has been remeasured to beT1/2=0·32±0·02 ns using γ-γ delayed coincidences. Electromagnetic properties of the various levels calculated on the core-particle coupling model agree with the experimental results. The results are compared with other existing theoretical calculations.

TRANSIENT FIELD MEASUREMENT IN THE GIANT MOMENT PDFE ALLOY

Abstract The transient magnetic field (TF) for oxygen ions using the 16 O(3 − ) nuclear state as probe has been measured for the first time in the polycrystalline Pd 3 Fe ferromagnetic alloy. The measured value of the TF, associated with the polarized 1s-electron, has a strength B TF =169 (50) T corresponding to a degree of polarization of p 1s =0.058 (17). The results are in good agreement with calculations based on the spin exchange model. One concludes from these measurements, that the mean magnetization per host atom is responsible for the magnitude of the probes polarization.

Strong double K-K transfer channel in near symmetric collision of Si+Ar at intermediate velocity range

We present a combined study of single and double K-K electron transfer cross sections along with the single and double K-shell ionization of Ar induced by Si projectiles in the energy range 0.9-4.0 MeV u-1 . The charge-state dependence of the normal and hypersatellite x-rays was used to derive the cross sections for the one- and two-electron processes, respectively. The enhancement in the fluorescence yields due to multiple vacancies was measured from the energy shifts and intensity ratios of the characteristic x-ray lines to derive K-shell vacancy production cross sections from x-ray production cross sections. The ratio of double to single K-K transfer cross sections is found to be quite large for this nearly symmetric collision system, whereas the ratio of double to single ionization cross sections is quite small. The measured single K-K transfer cross sections are reproduced very well by the two-centre close-coupling calculations whereas the double K-K transfer data are underestimated by the theory based on the independent-electron approximation (IEA). The K-shell ionization cross sections are found to deviate strongly from the calculations based on the continuum distorted wave eikonal initial state (CDW-EIS) and ECPSSR models. The CDW-EIS calculations along with the IEA model grossly underestimate the double ionization cross sections. It is stressed that in the case of two-electron processes the independent-electron model breaks down and the possible role of correlations between K-electrons is discussed.

Study of x-ray and L-REC photon emissions from highly ionized swift and projectiles passing through a thin carbon foil

X-rays and L-shell radiative electron capture (L-REC) photons have been detected from highly ionized swift projectiles of and passing through a thin carbon foil at two incident projectile energies. All the K and L peaks show strong shifts towards higher energy as a result of multiple ionization of L- and M-shells. The intensity ratios have been found to be almost half of the value for the singly ionized atoms. The measured positions of various L and K x-ray peaks and the measured intensity ratios have been attributed to certain types of electronic configurations based on the extensive multiconfiguration Dirac-Fock calculations. Generally, it has been found that the lowest-energy configuration plays a rather small role, but in contrast the excited configurations with holes in the L-shell and with occupied 3d, 4s, 4p, 4d or higher subshells seem to be very important. The relative L-REC cross section between higher and lower projectile energies shows excellent agreement with the results obtained under the non-relativistic dipole approximation.

A triple axes multiple target holder assembly

A triple axes multiple target holder assembly has been designed and fabricated to accommodate 27 targets to be used inside a high vacuum scattering chamber. This target holder assembly has been used satisfactorily in ion solid collision experiments using heavy ion beams from an accelerator.

Subshell-resolved L - K electron transfer and ionization cross sections for Au by bare and H-like sulphur ions

We have measured, for the first time, subshell-resolved L - K ( - K, - K and - K) electron transfer cross sections for electron transfer from the L-shell of the target to the vacant K-shell of the projectile. These cross sections are derived by measuring the charge-state dependence of the target L x-rays from a thin Au target using bare and H-like sulphur ions. In addition, the subshell-resolved ionization cross sections are also derived from the analysis of the L x-ray production cross sections. We found that the vacancy production cross section for the subshell is much smaller than that for strongly bound subshell and the - K transfer cross section is also much smaller than the - K transfer cross section. These observations are contrary to the prediction of first-order theories.

A simple post-accelerator foil stripper assembly for atomic collision experiments

A multiple foil holder for use in ultra high vacuum (UHV) environment as a post accelerator ion stripper has been designed and fabricated. It is used to produce beams of an ion in different charge states at a given energy from a 14 MV pelletron accelerator. These ions are required in several types of atomic collision experiments. The assembly is tested with32S ions at various energies.

L X-RAYS FROM 64 MEV IODINE PROJECTILES IN COLLISION WITH VARIOUS GAS TARGETS

L x-rays from 64 MeV iodine projectiles in collision with various gas targets, , have been studied. The x-ray intensity ratio is found to be weakly dependent on between and Ar, in contrast to a sharp decrease between C and Al, reported by Datz et al using thick solid targets. Differences in the measured intensity ratio of iodine with 7+ and 24+ charge states impinging on Kr target establishes the minor role of the electrons in the N shell of the projectile in the x-ray production mechanism. The data also support the MO correlation rule of Eichler et al for the asymmetric collision systems.

K-shell ionization of high Z elements with low to intermediate velocity Si ions

We report here the measurement of the absolute cross-sections for the K-shell ionization of high atomic number elements (Au and Bi) induced by low to intermediate velocity Si ions. The relativistic wavefunction effects on the ionization cross-sections have been studied by comparing the measured data with different theoretical calculations with and without including the relativistic corrections. The relativistic effect on the K-ionization cross-section is found to depend on the projectile atomic number and velocity.